It is known that perioperative pain may be reduced by beginning pain reduction therapy before surgery. This early intervention therapy is commonly known as preemptive analgesia, the purpose of which is to reduce the hypersensitization of nociceptors by blocking pain impulses from ever reaching the brain. Essentially, preemptive analgesia prevents the activation of the nociceptors before activation can occur.
Preemptive analgesia has received widespread acceptance as an adjunct to reduce perioperative pain in patients who undergo surgical procedures as generally disclosed by Mayer et al. in U.S. Pat. No. 5,502,058. The technique is well accepted and involves the pharmacological interruption of afferent neurons to the dorsal horns of the spinal cord prior to the delivery of painful stimuli, such as a surgical incision. The anesthetic concept can be applied to most surgical procedures, minimizing postoperative pain as well as the necessity for narcotic or parenteral analgesia. Moreover, patients treated with preemptive analgesia have experienced reduced hospitalizations and a much shorter convalescence.
A clinical shortcoming of preemptive analgesia, however, has been the relatively short duration of the local anesthetic, lidocaine hydrochloride (HCl), which is considered standard and customary. Lidocaine has a very short half-life (less than 30 minutes) and has no inherent contribution to pain control once its local anesthetic effect has resolved. However, lidocaine HCL's extremely rapid onset of action (less than one minute) characterizes it as an attractive agent for neural blockade.